The invention relates to a sieve belt composed of a multiplicity of helices of thermosettable synthetic resin monofilament in which adjacent helices are interlocked such that the windings of one helix enter between the windings of the adjacent helix, and having a pintle passed through the channel formed by adjacent helices.
In a sieve belt as taught in German Offenlegungsschrift No. 2,419,751 the helices, after their windings are interlocked, exhibit bias similar to a tension spring urging adjacent windings against each other. This bias is caused by the use of closely wound helices. In order to be interlocked, these helices must be stretched until the windings of one helix can enter between the windings of the adjacent helix. In operation, for example in a paper making machine, the sieve belt runs over rolls, causing the helices to "hinge" about the inserted pintle-filament. The contacting sides of the interlocking windings thus move relative to each other, resulting in friction and wear. This limits the service life of the known sieve belt. Furthermore, in the known sieve belt the diameter of the channel through which the pintle-filament is inserted must be greater than the diameter of the pintle-filament. For this reason the helices must be oval to begin with, and in cross section of the helices the inner clearance between the nearly parallel portions or legs of the ovals must be greater than the diameter of the inserted pintle-filament. As a consequence, grooves are formed in the surface of the finished sieve belt which extend parallel to the inserted pintle-filaments and leave marks in the paper. Moreover, there is a great deal of free space between the helices which results in non-uniform permeability. Furthermore, the helices in the known sieve belt possess a degree of torsion, i.e. in each winding the synthetic resin filament is turned once about its longitudinal axis. This torsion results in the deformation and distortion of the synthetic resin filament and also of the helices formed therefrom. This distortion of the helices complicates production of the sieve belt and detracts from its ability to resist pileup during use.